Scleral buckling band and method for making the same

ABSTRACT

A scleral buckling band and a method for making the same are described. The scleral buckling band is used for an ophthalmic operation, which is biocompatible and has a slender cylindrical structure formed by a decomposable and absorbable material. When being implanted into human body, the scleral buckling band is degraded and absorbed by the human body, without causing any immune response. After the patient is recovered, the scleral buckling band does not need to be taken out through another operation. Meanwhile, the decomposition rate of the scleral buckling band within the human body can be controlled through different preparation manners, so as to cater to different recovery speeds of different patients. Furthermore, the scleral buckling band contains different medicine, and after being implanted into human body and being decomposed, the scleral buckling band releases different specific medicine as time elapsed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a scleral buckling band and a methodfor making the same, in particular, to a scleral buckling band used foran ophthalmic operation, which is biocompatible and capable of beingdecomposed and adsorbed by human body.

2. Related Art

Retinal detachment is considered as the main reason for causingblindness. Due to retinal detachment, the retinal photoreceptor cellscannot obtain nutrition from the choroids. If the detachment lasts for along time, the retinal atrophy may occur, which results in blindness.Currently, the methods used for clinically curing the retinal detachmentmainly include operation, laser, freezing, or repair of pneumaticretinopexy, which aim at recovering the detached retina and curing theretinal tears, and meanwhile firmly joining the retina and choroidstogether.

In the above and relevant methods for curing retinal detachment, ascleral buckling operation is needed. Currently, most of the scleralbuckling bands 1′ used in the operation are made of silicone andhydrogel materials. However, such buckling materials cannot bedecomposed and absorbed by human body, and even causes rejectionresponse. Therefore, when the patient is recovered, the scleral bucklingband has to be taken out through another operation, which causes manyinconveniences and resource waste.

Accordingly, till now, it still needs a scleral buckling band that isdecomposed and absorbed by human body naturally after being implantedinto human body, without causing any immune response and without theproblem of rejection response or requiring another operation forremoving the implant.

SUMMARY OF THE INVENTION

In order to solve the problems in the prior art, the present inventionis directed to a scleral buckling band used for an ophthalmic operation.The scleral buckling band has a slender cylindrical structure formed bya biocompatible, decomposable, and absorbable material. After beingimplanted into human body, the scleral buckling band is degraded andabsorbed by the human body, without causing any immune response. Thepresent invention is further directed to a scleral buckling bandcontaining medicine, which releases specific medicaments required bydifferent periods of treatment as time elapsed.

The present invention provides a scleral buckling band containingmedicine. The medicine includes an anti-microbial agent, ananti-inflammatory agent, a guided tissue growth factor, or anothersuitable medicine. The scleral buckling band carries specificmedicaments according to the patients' different requirements, whichenhances the medicament delivery efficiency.

The scleral buckling band of the present invention is made by combiningcollagens having different strengths with different medicaments to becontained in the scleral buckling band. Since different collagens withdifferent strengths have different decomposition rates and differentmedicaments are contained, the scleral buckling band releases specificmedicaments required in different periods of treatment as time elapsed,which thus enhances the barrier effect, and improves the effects ofwound healing and tissue regeneration. The present invention is furtherdirected to a method for making a scleral buckling band. In order toachieve the above objects, the present invention provides a scleralbuckling band with different strengths, which is made of collagenshaving different strengths. The collagens having different strengths areprepared according to the content of collagens, type and cross-linkingmanner of the cross-linker.

The scleral buckling band of the present invention used for anophthalmic operation is degraded and absorbed by human body after beingimplanted into the human body, without causing any immune response. Inaddition, the scleral buckling band does not need to be taken outthrough another operation after the patient is recovered, and it furthercarries specific medicaments according to different demands of thepatients, which improves the delivery efficiency of the medicaments.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given herein below for illustration only, whichthus is not limitative of the present invention, and wherein:

FIG. 1 is a schematic structural view of a scleral buckling bandaccording to the present invention;

FIG. 2 is a coordinate graph of tensile strength test results of thescleral buckling band according to the present invention;

FIG. 3 shows a picture of a microscopic structure of the scleralbuckling band according to the present invention;

FIG. 4 shows a picture of animal experiment of the scleral buckling bandaccording to the present invention;

FIG. 5 shows a picture of animal experiment of a scleral buckling bandin the prior art; and

FIG. 6 is a bar graph about distortions of eyeballs through implantingthe scleral buckling band of the present invention comprised with thatin the prior art.

DETAILED DESCRIPTION OF THE INVENTION

In order to make the main technical features and functions of thepresent invention more comprehensible, the present invention is furtherdescribed below in detail with reference to the accompanying drawings.

Preparation of Type I Collagen

1. A bovine skin and tendon enriched with collagens were cut into cubeswith a size of about 0.5 cm³, placed into 10 L 95% alcohol, and stirredat 4° C. for 24 h. The bovine tendon was taken out of the 95% alcohol,placed into 10 L 0.5 M acetic acid solution, and then stirred at 4° C.for 72 h. Then, pepsin (SIGMA P7000, 4000 unit/ml) was added, and thesolution was continuously stirred at 4° C. for 24 h.

2. The mixture of Step 1 was filtered with a stainless steel mesh toremove the undecomposed residues. Sodium chloride was added continuouslytill the concentration thereof reached 1.0 M, and then the solution wasstirred at 4° C. for 30 min and centrifuged at a rotation speed of10,000 g (Beckman Avanti J-20) for 30 min.

3. After removing the supernatant, 10 L 50 mM Tris-HCl buffer (pH 7.4)was added, and stirred at 4° C. for 30 min. Then, sodium chloride wasadded again till the concentration thereof reached 4.0 M. The solutionwas stirred at 4° C. for 30 min, and then centrifuged at a rotationspeed of 10,000 g for 30 min.

4. After removing the supernatant, 10 L 50 mM Tris-HCl buffer (pH 7.4)was added, and stirred at 4° C. for 30 min. Then, sodium chloride wasadded again till the concentration thereof reached 2.5M. The solutionwas stirred at 4° C. for 30 min, and then centrifuged at a rotationspeed of 10,000 g for 30 min.

5. After removing the supernatant, 5 L of a mixed solution ofisopropanol and pure water (Isopropanol: H₂O=1:4) was added, stirred at4° C. for 30 min, and then centrifuged at a rotation speed of 10,000 gfor 30 min. This step was repeated twice.

6. After removing the supernatant, 5 L 0.05M acetic acid solution wasadded, and stirred thoroughly and uniformly and then placed at atemperature of −90° C. for being frozen. Then, the congelation was driedwith a freeze dryer to a constant weight. The resulted dry product istype I collagen.

Preparation of Scleral Buckling Band

1. The type I collagen was added into a weak acidic aqueous solution(for example, 0.05 M aqueous acetic acid solution), and stirred at ahigh speed into a homogenous slurry, in which the slurry contains thetype I collagen at a concentration of about 2 wt %. Then,glycosaminoglycans (GAGs) were dissolved into the weak acidic aqueoussolution (for example, 0.05 M aqueous acetic acid solution) to get anaqueous solution at a weight concentration of about 0.4 wt %-1.0 wt %.

2. The aqueous GAGs solution was mixed with the type I collagen slurry,in which the ratio of the GAGs was about 2.0 wt %-5.0 wt % based on theweight of the type I collagen, and then placed at room temperature for48 h to remove a part of the moisture, so as to get a thicker slurrymixture. Then, the resulted slurry mixture was made to pass throughneedle heads with a diameter of 0.9 mm and 0.5 mm to become homogenous.Then, the mixture was filled into a mold for making the scleral bucklingband. Sequentially, a vacuum freeze-drying treatment was performed forabout 36 h to remove the moisture in the solution. Then, the mixture washeated at 105° C. in vacuum for 24 h, so as to be thermal dehydrated andcross-linked, and then, the 260 nm UV cross-link treatment was performedto get a predetermined scleral buckling band. Thereafter, a cross-linktreatment was performed with a natural cross-linker (genipin) orglutaraldehyde, such that the collagen and the GAGs were cross-linked,so as to enhance the mechanical strength of the scleral buckling band,thereby the decomposition rate thereof was controlled. Finally, thescleral buckling band was washed with pure water and freeze dried to geta scleral buckling band with a slender cylindrical structure, as shownin FIG. 1.

Mechanical Property Test of Scleral Buckling Band

The resulted scleral buckling band (with a length of 5.0 cm, a diameterof 0.2 cm) is fixed on clamps of a material testing machine. The testlength of the scleral buckling band confined between two clamps is 3.0cm, and then a force is applied to stretch the scleral buckling band,till the scleral buckling band is broken. The force applied at theinstance when the scleral buckling band is broken is recorded, and thetensile strength of the scleral buckling band is calculated as 2.37 MPa,as shown in FIG. 2.

Observation of the Scleral Buckling Band with Microscope

The resulted scleral buckling band is observed with a scanningelectronic microscope (SEM), and the average porosity of the scleralbuckling band is calculated to be about 120±40 μm, as shown in FIG. 3.

As polymer materials are easily processed and have high mechanicalstrength and desirable biocompatibility, they have been widely used todevelop thousands of medical products, such as disposable medicalequipments and implantable biomedical materials in the past decade.

Natural polymers include collagen and polysaccharide biopolymer, forexample, hyaluronic acid (HA) and chitosan, and chemical syntheticpolymers include polylactic acid (PLA), polyglycolic acid (PGA), andpolylactic acid-glycolic acid (PLGA).

The PLA, PGA, and PLGA are all bio-absorbable polymer materials withdesirable biocompatibility, and their co-polymers are decomposed intosmall molecular chain segments in a living body, and then discharged outof the living body as the metabolism process continues. Therefore, thePLA, PGA, and PLGA have desirable biocompatibility, bio-absorbability,and capable of being discharged out of the body as the metabolismprocess continues, which thus can be processed into different types ofimplantable biomedical materials with slow degradability and capable ofreleasing different coated medicaments.

HA is a polysaccharide biopolymer and widely exists in connectivetissues, mucous tissues of vertebrates, crystalline lens of eyeballs,and capsules of some bacteria in the nature. Regardless of the source,the chemical composition and structure of HA are the same. Therefore, ifHA is used as a medical polymer material, it can be decomposed andabsorbed by the living body, without causing any immune response.Recently, HA has been gradually developed for the applications ofpost-operation tissue anti-adhesion and medicament release.

Chitosan is a biopolymer prepared by extracting from natural biologicalorganism, and mostly exists in crustacean, which has desirablebiocompatibility with cells of biological organisms, has no toxicity,and can be decomposed by biological organisms, and thus it can bedeveloped as a carrier for drug release.

Collagen is a polymer for forming various extra-cellular matrixes andserves as combination tissues in animal cells. Collagen mainly exists inthe form of an insoluble fibrin, and takes about 25%-30% of the proteinsin human body. Therefore, the collagen has desirable biocompatibility,and can prevent human body from generating rejection response and can beabsorbed by the tissues after being decomposed. The collagen can beextracted and purified from biological tissues. Then, the mechanicalstrength of the material can be enhanced by physical or chemicalcross-linking treatment, and can also be made into a porous structure,which is suitable for being used as a temporary tissue filling materialand can also be made into a base material for various artificialtissues.

According to the present invention, the material for making the scleralbuckling band includes, but not limited to, collagen, PLA, PGA, PLGA,PCL, HA, and chitosan, and another polymer material. Preferably, thematerial is collagen.

According to the present invention, the scleral buckling band may havedifferent strengths, and when an oculist performs an operation, thescleral buckling bands with different strengths may be selected tocontrol the residence time of the scleral buckling band within the humanbody, so as to cater to different recovery speeds of different patients.It is known to those of ordinary skill in the art that, collagens withdifferent strengths can be made according to the content of collagens,type and cross-linking manner of the cross-linker. However, the presentinvention is not intended to limit the content of collagens, type, andcross-lining manner of the cross-linker. The conventional methods formaking collagens with different strengths all can be used in the presentinvention for making the scleral buckling band.

Referring to FIGS. 4 and 5, the distortion of eyeballs is measured bysonography as time elapsed. As the conventional scleral buckling bandused in the operation is made of silicon, it cannot be metabolized anddecomposed by enzymes and other substances within the human body, sothat the buckling effect generated on the sclera after the scleralbuckling band is implanted lasts for a long time, and the eyeballmaintains a certain distortion, as a result, the vision is affected. Thescleral buckling band of the present invention is mainly made ofcollagens and is metabolized and decomposed by the enzymes within thebody, and accordingly, after the scleral buckling band is implanted, thebuckling effect on the sclera is decreased as time elapsed. Besidesachieving the functions of the conventional scleral buckling band, thescleral buckling band further makes the distortion of the eyeball bedecreased as time elapsed, which means that the eyeballs return to theoriginal shape, as shown in FIG. 6, so that the scleral buckling band ofthe present invention does not bring any influences on vision.

According to the present invention, the scleral buckling band optionallycontains medicaments, such as an anti-microbial agent, ananti-inflammatory agent, a growth factor, or another suitable medicine.It is well known to those skilled in the art that, the polymerbiomedical material is characterized in containing therapeutic orpreventive medicaments therein when being prepared. The commonbiomedical materials are generally applied on parts under operation orwounds, and carry specific medicaments according to differentrequirements of different patients through the function of carryingdrugs, so as to enhance the delivery efficiency of the medicaments.

According to the present invention, the scleral buckling band is made bycombining collagens with different strengths and contains differentmedicaments, and since the collagens with different strengths havedifferent decomposition rates and different medicaments are containedtherein, the scleral buckling band releases specific medicamentsrequired by different periods of treatment as time elapsed, which thusenhances the barrier effect, and improves the effects of wound healingand tissue regeneration.

In view of the above, the scleral buckling band of the present inventioncan be industrialized and has novelty and inventive step, and thus meetsthe patent requirements. The above description is merely a preferredembodiment of the present invention, but not intended to limit the scopeof the present invention.

1. A scleral buckling band, used for an ophthalmic operation, comprisinga slender cylindrical structure formed by a biocompatible material. 2.The scleral buckling band according to claim 1, wherein thebiocompatible material is selected from a group consisting of collagen,polylactic acid (PLA), polyglycolic acid (PGA), polylactic acid-glycolicacid (PLGA), polycaprolactone polyol (PCL), hyaluronic acid (HA), andchitosan.
 3. The scleral buckling band according to claim 1, wherein thebiocompatible material is collagen.
 4. The scleral buckling bandaccording to claim 3, wherein a strength of the scleral buckling band isadjusted according to a content of collagens, type and cross-linkingmanner of a cross-linker, so as to control a residence time of thescleral buckling band within the human body.
 5. The scleral bucklingband according to claim 1, further containing medicine.
 6. The scleralbuckling band according to claim 1, further containing specificmedicaments released in different periods of treatment as time elapsed.7. The scleral buckling band according to claim 6, wherein the specificmedicament is an anti-microbial agent, an anti-inflammatory agent, or aguided tissue growth factor, or another suitable medicine.
 8. A methodfor making a scleral buckling band, at least comprising: preparing abiocompatible material; filling the biocompatible material into a mold;performing a vacuum freeze-drying treatment to remove moistures in thebiocompatible material; and performing a ultraviolet (UV) cross-linkingtreatment to obtain a predetermined slender cylindrical structure. 9.The method for making a scleral buckling band according to claim 8,wherein the biocompatible material is selected from a group consistingof collagen, PLA, PGA, PLGA, PCL, HA, and chitosan.
 10. The method formaking a scleral buckling band according to claim 8, wherein thebiocompatible material is formed by mixing an aqueous solution ofglycosaminoglycans (GAGs) with a collagen slurry, and then placing themixture at room temperature to remove a part of the moisture in themixture, so as to get a slurry mixture, wherein the ratio of theglycosaminoglycans is about 2 wt %-5 wt % based on a weight of thecollagen.